Belt printer

ABSTRACT

A high speed printer including a bank of aligned individually actuatable hammers and a type surface mounted for movement opposite to and along said line of hammers. The type surface is comprised of unit type areas formed on the end surfaces of elongated slugs carried by a flexible band. The band is supported on a roadbed formed by low friction bearings and including a drive wheel for driving the band around the roadbed. The slugs are fixed to the band by an elastic damping material to minimize interaction between slugs. Permanent magnets are employed to establish a field passing through the slugs to increase contact pressure between the band and roadbed bearings and to facilitate positional restoration of the slugs after hammer impact.

United States Patent 11 1 1111 3,845,711

Helms Nov. 5, 1974 i 1 BELT PRINTER Primary Examiner-Robert E. Pulfrey Assistant ExaminerEdward M. Coven [75] lnvcmor' m Helms calldbdsds Park Attorney, Agent, or Firm-Lindenberg, Freilich,

- Wasserman, Rosen & Fernandez, [73] Assignee: Data Products Corporation,

Woodland Hills, Calif. I [57] AESTRACT [22] F1lcd: Dec. 13, 1972 i A high speed prmter 1r1clud1ng a bank of aligned indil l PP N04 3141693 vidually actuatable hammers and a type surface mounted for movement opposite to and along said line [52] Cl. 101/111, lOl/93 C of hammers The p Surface is Comprised of unit [51] Int. Cl 341i 9/08 type areas formed on the end Surfaces of elongated 58 Field 01 Search 101/111, 93 c Slugs carried by flexible band- The band is Supported on a roadbed formed by low friction bearings and in- 5 R f e Cited eluding a drive wheel for driving the band around the UNITED STATES PATENTS roadbed. The slugs are fired to the band by an elastic 7 l2 9 C h. damping materlal to mmimize interaction between 5: g slugs. Permanent magnets are employed to establish a f 5/1968 Foey 4 10U93 C field passing through the slugs to increase contact 3:435:756 4/1969 Mai-unlit: III: 101 93 c Pressure between the band and madbsd bearings and 3499383 3/1970 PM et aL D p v H 101 /93 C to facilitate positional restoration of the slugs after 3,621,778 11 1971 Ripple et al. 101/111 x hflmmfif p 3,683 802 8/1972 Hepner et al 1. lOl/l ll 12 Claims, 5 Drawing Figures P v 5mm .AIENIEDIn sum 20 3 BELT rnrnraa BACKGROUND OF THE INVENTION This invention relates generally to high speed printers and more particularly to an improved type assembly for use therein for presenting type characters to a print station.

The prior art is replete with various high speed printer mechanisms, many of which employ individually actuatable hammers which impact against selected characters on a moving type surface to print the characters on a paper therebetween. Such impact printers may be classified in accordance with the kind of type assembly utilized to present type characters to the hammers. Thus, a first class utilizes a drum mounted to rotate about an axis extending parallel to the line of hammers. Type characters formed on the periphery of the drum are arranged in annular tracks, each track containing a full character set and being aligned with a different hammer. In this configuration, since the drum surface moves perpendicularly to the print line, when a hammer impacts against the drum, sandwiching the paper and ribbon therebetween, the drum motion tends to drag the paper in a direcion perpendicular to the print line. As a consequence, slight vertical misregistrations often occur amongst the'printed characters in a horizontal line.

A second class of impact printers utilizes a type assembly in which the type surface moves horizontally along the line defined by the hammers. In this configuration, during impact, the moving type surface tends to drag the paper along the print line. Since the resulting horizontal errors produced are not nearly as apparent to the eye as the previously mentioned vertical misreg istrations, it is generally considered that at high speeds, e.g., above 1,500 lines per minute, printers of this second class are inherently capable of producing a higher print quality than printers of the first mentioned class. However, since considerably greater mechanical complexity is required to provide a type surface moving horizontally along the hammer line than to provide the previously mentioned drum, printers of the aforementioned second class have been somewhat less reliable and more expensive than printers of the aforementioned first class.

SUMMARY OF THE INVENTION The present invention is directed to a high speed printer utilizing an improved type assembly of the kind in which the type surface moves horizontally along a hammer line.

In accordance with the preferred embodiment of the invention, the type surface is comprised of a plurality of unit type areas, each formed on the end surface of an elongated type slug. A. plurality of type slugs are carried by a flexible band which is supported on a low friction roadbed. In accordance with one preferred aspect of the invention, the'band is formed so as to be flexible about an axis extending perpendicular to its direction of movement but semi-rigid about a line extending parallel to its direction of movement.

In accordance with another preferred aspect. of the invention, type slugs are employed each having a mass much greater than that of a hammer so as to minimize energy transfer from a hammer to a slug. Moreover, the slugs are elongated in a direction in line with the flight of the hammers so that impact tends to produce an almost longitudinal displacement of a slug thereby minimizing the likelihood of slug misalignment. This assures uniformity of print density and character spacing.

In accordance with a further preferred aspect of the invention, each slug is fixed to the band by an elastic damping material so as to minimize interaction between slugs.

In accordance with a still further preferred aspect of the invention, permanent magnets are utilized to estab-. lish a field passing through the slugs to increase contact pressure between the band and the roadbed bearings and to facilitate positional restoration of the slugs after hammer impact.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of a. high speed printer in accordance with the present invention;

FIG. 2 is a front plan view of a preferred embodiment of type assembly in accordance with the present invention;

FIG. 3 is a sectional view takensubstantially along the plane 33 of FIG. 2;

FIG. 4 is a perspective view illustrating a preferred roadbed embodiment upon which the character band of FIGS. 2 and 3 rides; and

FIG. 5 is a perspective view of the band utilized in FIGS. 2 and 3 shown without the type slugs attached thereto.

Attention is now called to FIG. I which ilustrates a high speed impact printer exemplary of the type generally employed for data processing applications. Briefly,

the printer of FIG. I is comprised of a first frame 10 supporting both a hammer bank assembly l2 and a paper stepping system generally comprised of tractor chains I4, driven by motor I15. The chains I4- pull edge perforated paper 116 from a supply stack 18 past the impact faces 20 of the hammer bank assembly I2. A typical hammer bank assembly is disclosed in US. Pat. No. 3,643,595 issued Feb. 22, I972.

The printer of FIG. I also includes a second frame 30 which is hinged with respect to the first frame It) about a hinge pin 311. Cooperating latch mechanisms M) and 42 are carried respectively by the frames Ill and 30 for locking the frames together in closed operative relationship.

The frame 30 supports a type assembly 32 which includes a moveable type bearing surface which presents successive type characters to the hammer impact faces ZIP, The present invention is directed primarily to an improved type assembly in which the type bearing surface moves horizontally along the line of hammer impact faces. The details of a type assembly in accordance with the invention will be discussed hereinafter subsequent to a brief consideration of the operation of the printer of FIG. II.

In operation, the edge perforations of the paper 16 are engaged with the sprockets of chains I4 and the frame 39 is in a closed latched position with respect to the frame Id. Movement of the chains by the motor 15 pulls the paper past the hammer impact faces 20 one line at a time. In this closed operative position, the hammer impact faces are disposed very close to the paper In which in turn is disposed very close to a printing ribbon 44 carried by frame 36 adjacent to the type assembly 32. As will be seen hereinafter, as the type surface of the assembly 32 is moved, it presents successive type characters to each of the plurality of print stations, i.e., the hammer impact faces. By actuating a hammer at an appropriate time, the hammer impact face is propelled against the back side of the paper 16 forcing the paper against the ribbon 44 and the type surface of assembly 32 to thus print the struck character on the front side of the paper.

As previously mentioned, the present invention is directed primarily to an improved type assembly 32 for successively presenting characters to be printed to the print stations. Briefly, a type assembly in accordance with the invention is comprised of an endless band 50 supported on a roadbed formed by low friction bearings such as roller bearings. The roller bearings bear outwardly against the inner surface of the band 50 and means are provided for driving the band around the roadbed. As can be seen in FIG. 1, type slugs 52 are carried on the outer surface of the band. Each type slug has a type character area formed on at least one end thereof and as the band is moved around the roadbed, successive characters are presented at each print station.

Attention is now called to FIGS. 2-5 which illustrate the type assembly 32 in greater detail. The assembly includes an endless band 50 having inner and outer peripheral surfaces 54 and 56. The band 50 preferably has an I-shaped cross section, as is best shown in FIG. 3, comprised of enlarged end portions 58 and 60 and a central trough portion 62. The band 50 preferably comprises a plastic material such as polyurethane formed around a flat steel belt 64. As a consequence of this construction, the band 50 will exhibit the desirable characteristics of being relatively flexible about an axis extending parallel to the bands axial direction and being relatively rigid about a line coincident with the circumference of the band.

In accordance with the preferred embodiment of the invention illustrated, the roadbed for the band is formed by the plurality of roller bearings 66 together with an idler pulley 68 and a drive wheel 70. More particularly, as is best shown in FIG. 4, a central frame 72 is provided for supporting the roadbed bearings. The frame 72 defines a plurality of slots 74 onthe upper surface thereof, each of which is adapted to receive the spindle 76 of a pair of roller bearings 78 and 80. The roller bearings 78 and 80 of each pair are spaced along the spindle by a distance substantially equal to the width of the band 50 to enable them to respectively engage the enlarged end portions 58 and 60 of the band as shown in FIG. 3. Both the idler pulley 68 and the drive wheel 70 are mounted for rotation about an axes extending parallel to the spindles 76. The axial dimension of the idler pulley and drive wheel circumferential surfaces is selected to be substantially equal to the width of the band trough 62 so that with the band placed on the roadbed as illustrated in FIG. 2, the circumferential surfaces of the idler pulley 68 and drive wheel 70 will engage the inner surface 54 of the band trough 62. I

In order to facilitate placement of the band on and removal of the band from the roadbed, the axle 82 of the idler pulley 68 is mounted so that it can be moved toward and away from the fixed axle 84 of drive wheel 70. That is, in order to place the band 50 on the roadbed, the distance between'the axles 82 and 84 is initially minimized. The band is then placed on the roadbed with the inner surface 54 of the enlarged end portions 58 and 60 engaging the outer races of roller bearings 78 and 80 and with the inner surface of band trough 62 engaged with the circumferential surface of drive wheel 70. The axle 82 is then moved away from the axle 84 to bring the circumferential surface of idler pulley 68 into engagement with the inner surface of the band trough 62. The axle 82 is then locked into position with the bearings 78 and 80, idler pulley 68 and drive wheel all bearing against the inner surface of the band 50.

In addition to the roller bearings 78 and mounted for rotation about horizontally oriented spindles as shown in FIG. 3, a plurality of roller bearings 86 are provided, each mounted for rotation about a vertical spindle. The outer races of bearings 86 engage the edge surface 88 of the enlarged band end portions 58 as illustrated in FIG. 3.

As is best shown in FIGS. 2 and 3, a plurality of elongated type slugs 52 are secured to the outer surface 56 of the band extending in an axial direction. Each slug 52 preferably has a rectangular cross section and defines a type character area 90 on one end thereof opposed to the hammer impact faces 20 when the frames 10 and 30 of FIG. 1 are in a closed latched position. Each of the character areas 90 has a raised type character formed thereon.

The type slugs are selected so as to have a large mass relative to the mass of the hammer in order to minimize the energy transfer from a hammer to a slug upon impact. Preferably, the mass of each slug will be atleast five to 10 times the mass of a hammer. The slugs preferably have a rectangular cross section as shown in FIG. 2 in order to maximize the mass of the slug within the constraints of its overall dimensions. The maximum width dimension of a slug character is of course determined by the desired spacing between printed characters. Typically, the width of a character area would be approximately 0.09 inches with a 0.125 inch spacing being utilized from center to center of adjacent slugs. Typically, the height of a slug character area would be approximately 0.3 inches. The length of a slug 52 is selected so as to assure sufficient mass within the slug to achieve the aforementioned ratio of slug to hammer mass. Typically, the slug will be approximately 2 inches long.

The slugs 52 are attached to the band 50 by an elastic damping material such as butyl rubber 92 which is adheredboth to the trough portionof the outer surface 56 of the band 50 and to the underside of the slugs 52 as shown in FIG. 3. All of the slugs 52 are positioned on the band 50 so that the character areas 90 reside in a substantially common plane opposed to the common plane defined by the hammer impact faces.

The longitudinal axes of the slugs 52 extend parallel to the flight paths of the hammers and the slugs are oriented so as to be struck'by the hammer impact faces very close to the center of gravity of the slug section. As a consequence, impact tends to displace the slugs in an almost true longitudinal direction thereby offering maximum resistance to slug misalignment or interaction between adjacent type slugs..Moreover, since each type slug 52 is suspended on an elastic damping material such as butyl rubber, interaction between slugs is minimized.

In accordance with a preferred aspect of the invention, a second character area'94 is formed on the end of each slug remote from the previously mentioned character area. Of course, only the character areas90,

as shown in FIG. 3, opposed to the hammer impact faces are used during printing. However, the band can be removed from the roadbed and reversed thereon to place the character areas 94 opposite to the hammer impact faces. Thus, a single band of slugs may for example be utilized to offer two different type fonts which can be selectively employed merely by reversing the orientation of the band on the assembly roadbed.

Typically, a band in accordance with the present invention will carry several sets of slugs on the outer surface thereof, each set containing a full complement of different character areas. For example, a typical character set may be comprised of 64 different characters with five sets of slugs (i.e. 564=320) being supported on a typical band. The rate at which the band must be driven around the roadbed by the drive wheel 70 depends of course upon the desired line print rate and the number of sets of slugs carried by the band. If, for example, it is desired to print at 1,200 lines per minute with a character spacing of 0. 125 inches, it is then necessary for the band to attain a linear speed of 160 inches per second. In order to assure the maintenance of good contact between the band and bearings at such high speeds, permanent magnet means are employed in accordance with the invention, to pull the band down onto the bearings. More particularly, as shown in FIGS. 2 and 3, permanent magnets 100 are supported within the frame 72 of the type assembly. The permanent magnets 100 generate a magnetic field represented by the arrows illustrated in FIG. 3, which is steered by magnetic plates 102 and 104 through the slugs 52; The slugs of course should be formed of a magnetic material such as a suitable iron alloy. The magnetic field thus produced through the slugs tends to pull the slugs toward the magnets thus increasing the rolling contact pressure between the band and the roadbed bearings 78 and 80. In addition, the magnetic fields tend to facilitate positional restoration of the slugs after hammer impact.

From the foregoing, it should now be appreciated that a high speed printer apparatus has been disclosed herein utilizing a type assembly inwhich a type bearing surface is moved horizontally along a line of print stations and wherein the type bearing surface is comprised of unit character areas formed on the ends of type slugs suspended on the outer surface of a flexible band mounted for rapid rotation on a low friction bearing roadbed. Although, in the preferred embodiment of the invention, the roadbed is formed by a plurality of roller bearings, it should be recognized that other types of bearings, such as air bearings, could be used without I departing from the spirit or scope of the invention.

What is claimed is:

l. A printing apparatus comprising:

hammer assembly means including a plurality of hammers mounted with the impact faces thereof defining a common elongated plane and means for individually actuating each hammer to propel the impact face thereof in a first direction substantially perpendicular to said plane;

means for transporting a web material to be printed upon along a path past said common plane of impact faces; and

type assembly means for successivelypresenting type characters to each of said hammer impact faces, said type assembly means including:

an endless band having inner and outer peripheral surfaces and characterized by being relatively flexible about an axis in the plane of said band perpendicular to its length and relatively rigid about an axis in the plane of said band parallel to its length;

a plurality of elongated slugs each. having a type character area on at least one end face thereof, each slug having a mass on the order of five times or more the mass of one of said hammers;

means fixing said slugs to the outer surface of said band with the length of said slugs extending across the width of said band and with said type character areas lying in a substantially common plane;

low friction bearing means engaging said band inner surface and supporting said ban-d with said plane of type character areas oriented substantially parallel to said plane of impact faces with said web material path disposed therebetween; and

means for driving said endless band around said low friction bearing means.

2. The printing apparatus of claim 1 wherein each of said slugs has a second type character area thereon at the end thereof remote from said first mentioned type character area.

3. The printing apparatus of claim 1 wherein said means fixing said slugs to said band includes elastic material attached to both said slugs and said band outer surface.

4. The printing apparatus of claim 1 wherein said low friction bearing means includes a plurality of roller bearings each including an outer race'engaged against said band inner surface and wherein said means for driving includes a drive wheel having a peripheral surface engaged against said band inner surface.

5. The printing apparatus of claim 1 including means for generating a magnetic field; and

means steering said magnetic field through said slugs for attracting said slugs toward said bearing means to thereby increase contact pressure between said band and said bearing means.

6. The printing apparatus of claim 4 wherein said endless band has front and rear edge surfaces and further including a second low friction bearing means engaging said band rear edge surface;

said second low friction bearing means including a plurality of roller bearings each including an outer race engaged against said band rear edge surface.

7. An assembly suitable for use in a printing apparatus for successively presenting type characters to a print station, said assembly comprising:

an endless band having inner and outer peripheral surfaces and characterized by being relatively flexible about an axis in the plane of said band perpendicular to its length and relatively rigid about an axis in the plane of said band parallel to its length;

7 8 disposed between said slugs and said band outer 10. The assembly of claim 7 including means generatsurface for minimizing interaction between said ing a magnetic field; and slugs and said band; an means steering said magnetic field through said slugs mealnsfor dnvlng Said endless band around 331d low for attracting said slugs toward said bearing means fncnon bearmg f to thereby increase contact pressure between said 8. The assembly of claim 7 wherein each of said slugs band and Said bearing means has a Second type cha'lacter area thereon at the end 11. The assembly of claim 7 wherein said endless thereof remote from said first mentioned type charac- {er area band comprises a flat steel belt enveloped by a plastic material.

9. The assembly of claim 7 wherein said low friction 10 bearing means includes a plurality of roller bearings The assembly of Glam 7 wherem endlfass each including an outer race engaged against said band band has from and e edge Surfaces and further inner surface and wherein said means for driving including a Second low friction bearing means engaging cludes a drive wheel having a peripheral surface ensaid band rear edge surface. gaged against said band inner surface. 5 

1. A printing apparatus comprising: hammer assembly means including a plurality of hammers mounted with the impact faces thereof defining a common elongated plane and means for individually actuating each hammer to propel the impact face thereof in a first direction substantially perpendicular to said plane; means for transporting a web material to be printed upon along a path past said common plane of impact faces; and type assembly means for successively presenting type characters to each of said hammer impact faces, said type assembly means including: an endless band having inner and outer peripheral surfaces and characterized by being relatively flexible about an axis in the plane of said band perpendicular to its length and relatively rigid about an axis in the plane of said band parallel to its length; a plurality of elongated slugs each having a type character area on at least one end face thereof, each slug having a mass on the order of five times or more the mass of one of said hammers; means fixing said slugs to the outer surface of said band with the length of said slugs extending across the width of said band and with said type character areas lying in a substantially common plane; low friction bearing means engaging said band inner surface and supporting said band with said plane of type character areas oriented substantially parallel to said plane of impact faces with said web material path disposed therebetween; and means for driving said endless band around said low friction bearing means.
 2. The printing apparatus of claim 1 wherein each of said slugs has a second type character area thereon at the end thereof remote from said first mentioned type character area.
 3. The printing apparatus of claim 1 wherein said means fixing said slugs to said band includes elastic material attached to both said slugs and said band outer surface.
 4. The printing apparatus of claim 1 wherein said low friction bearing means includes a plurality of roller bearings each including an outer race engaged against said band inner surface and wherein said means for driving includes a drive wheel having a peripheral surface engaged against said band inner surface.
 5. The printing apparatus of claim 1 including means for generating a magnetic field; and means steering said magnetic field through said slugs for attracting said slugs toward said bearing means to thereby increase contact pressure between said band and said bearing means.
 6. The printing apparatus of claim 4 wherein said endless band has front and rear edge surfaces and further including a second low friction bearing means engaging said band rear edge surface; said second low friction bearing means including a plurality of roller bearings each including an outer race engaged against said band rear edge surface.
 7. An assembly suitable for use in a printing apparatus for successively presenting type characters to a print station, said assembly comprising: an endless band having inner and outer peripheral surfaces and characterized by being relatively flexible about an axis in the plane of said band perpendicular to its length and relatively rigid about an axis in the plane of said band parallel to its length; low friction bearing means engaging said band inner surface and supporting said band thereon; a plurality of elongated slugs each having a type character area on one end thereof; means fixing said slugs to the outer surface of said band with the length of said slugs extending across the width of said band and with said type character areas lying in a substantially common plane, said fixing means including elastic damping material disposed between said slugs and said band outer surface for minimizing interaction between said slugs and said band; and means for driving said endless band around said low friction bearing means.
 8. The assembly of claim 7 wherein each of said slugs has a second type character area thereon at the end thereof remote from said first mentioned type character area.
 9. The assembly of claim 7 wherein said low friction bearing means includes a plurality of roller bearings each including an outer race engaged against said band inner surface and wherein said means for driving includes a drive wheel having a peripheral surface engaged against said band inner surface.
 10. The assembly of claim 7 including means generating a magnetic field; and means steering said magnetic field through said slugs for attracting said slugs toward said bearing means to thereby increase contact pressure between said band and said bearing means.
 11. The assembly of claim 7 wherein said endless band comprises a flat steel belt enveloped by a plastic material.
 12. The assembly of claim 7 wherein said endless band has front and rear edge surfaces and further including a second low friction bearing means engaging said band rear edge surface. 